1. Field of the Invention
This invention relates generally to pen injection devices, e.g., pre-loaded syringes, such as are utilized for injection of medicament into the body tissues of human and animal patients. More specifically, this invention relates to a removable pen needle which is more easily removed from the pen injection device. The pen needle can preferably include a safety system or shield to prevent inadvertent pricking on a user.
This invention also relates to a method of using pen needles for pen injection devices wherein the pen needle is configured to be used with conventional the pen injection device.
This invention also relates to a method of using pen injection devices more safely, i.e., preventing the user from being pricked when handling and/or attempting to remove the pen needle from the pen injection device.
2. Discussion of Background Information
U.S. Pat. No. 4,973,318, the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses a disposable syringe includes first and second housing elements which are coupled together for rotation without axial movement therebetween. The first housing element receives a cartridge of a solution to be injected, and mounts a liquid outlet needle at its front end. A piston rod is disposed in the second housing element to move axially therein, and this piston rod includes a rod element and a nut element. The rod element is coupled to the first housing element to move axially therein without relative rotation therewith, and the nut element is threaded to the rod element for telescoping movement therewith and is configured to move axially in the second housing element without relative rotation therein. A pressure receiving element is mounted on the nut element. The housing, rod, nut and pressure receiving elements cooperate such that relative rotation between the housing elements in a selected direction causes relative rotation between the nut and rod elements and thereby increases the effective length of the piston rod and causes the pressure receiving element to extend from the second housing element. A protective cap is removably mounted over the first housing element and is configured to abut second housing element while mounted in place on the first housing element. This protective cap is engaged with the first housing element such that rotation of the cap with respect to the second housing element causes rotation of the first housing element with respect to the second housing element.
This type of syringe is shown in FIGS. 1 and 2 wherein the pre-loaded syringe 1 has a proximal threaded end 2 which is configured to accept a needle tip assembly consisting of a needle tip 5, a needle tip cover, and a needle cover. A user installs the needle tip assembly 5 onto the end 2, after removing the assembly from its individual package, onto the threaded proximal end 2 by simply sliding it onto the end 2 axially. Because internal threads of the needle tip 5 are mounted to radially deflectable members, installation over threads of the end 2 occurs with a ratchet effect. This installation is made safe by the covers which ensure that the user will not be pricked by the needle N. Once installed, the user can remove the needle tip cover by simply sliding it off axially. Next, the user can remove the needle cover to expose the needle N. The pen needle device is then made ready for use in providing an injection to the user. After injection, the user will typically remove the needle tip 5 and discard the same. To accomplish the removal, the user will typically reinstall the needle tip cover and rotate it to cause the needle tip to unthread from the threaded end 2 (some users may even install the needle cover prior to installing the cover). Once removed, however, it is still possible to reinstall the used needle tip 5 by simply repeating the steps noted above. Unless the user discards the needle tip 5, it is possible that she or other users will not remember or know that it has already been used. That is, there is nothing to prevent reuse of the needle tip 5 should someone attempt to reinstall the needle tip onto the end 2. Furthermore, if the user is unable to locate the covers (i.e., if they have become lost), he/she must then attempt to grip the needle tip 5 in order to unthread it from the end 2. As is apparent, this action can be risky because the user can possibly inadvertently be pricked by the needle N either in attempting to properly grip the needle tip 5, in the action of rotating it to the point it is removed, or even in the handling of the needle tip 5 after it has been removed and prior to being properly discarded. Still further, if the needle tip 5 is not properly discarded (such as being correctly placed in a sharps container), others may come in contact with the needle tip 5 and possibly become injured thereby.
It is therefore desirable to provide a pen needle system which is safer to use compared to the conventional devices discussed above and/or which does not have one or more of the above-noted disadvantageous.